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Sécurité en plongée : attention au niveau élevé d'azote

There are many dangers to scuba diving. However, as long as you receive the proper training and follow the right precautions and procedures for handling such dangers, scuba diving should be a fun and safe sport that you can enjoy. One such danger which can be easily alleviated and managed given the right training and handling of procedures is nitrogen narcosis.

Nitrogen narcosis is a condition when a scuba diver becomes "high" or enters into an altered state of conscious while scuba diving. Nitrogen narcosis is actually misnamed. Scientific research has shown that almost every gas that can be breathed by humans, other than helium, can actually result in a narcotic effect. However, the effects of this particular narcosis was first observed with nitrogen inhalation which resulted in its naming.


Nitrogen narcosis is not dangerous in and of itself. The effects of nitrogen narcosis has been observed as being similar to intoxication due to alcohol. It is also easily alleviated by the diver going up to shallower depths. The main danger of nitrogen narcosis is the unpredictable behaviour of the diver who experiences it. The narcotic effect of nitrogen narcosis can range from a feeling of euphoria to paranoia. Other effects include the loss of focus and coordination, vertigo, exhaustion and other behavioural effects which tend to decrease the ability of the diver to perceive correctly and deal with his or her surroundings. The effects of nitrogen narcosis also increases as the scuba diver dives deeper. Therefore, once nitrogen narcosis is detected, a scuba diver should immediately move to shallower depths.

A large part of the problem of how to handle nitrogen narcosis is the varying effects it has on divers individually. One diver's experience of nitrogen narcosis will most like differ from another's experience. The effect of nitrogen narcosis can, however be detected individually if a diver gains enough experience with it. This has led to a misguided belief that one can train him or herself into tolerating nitrogen narcosis. This belief has no scientific basis and is particularly dangerous.

The depth in which nitrogen narcosis starts to affect divers also vary from case to case. Furthermore, the triggering depth of nitrogen narcosis can also differ from dive to dive. There is therefore no clear cut way for scuba divers to set their diving depth limits so as to avoid nitrogen narcosis. The only remaining option is, therefore to always be alert of the onset of nitrogen narcosis.

The most effective way that divers have found to manage nitrogen narcosis is to dive in pairs and to keep appraising each other's behaviour to see if either of them are beginning to succumb to nitrogen narcosis. A common practice among divers is to regularly do a "thumbs test" with each other. This involves the one diver showing the other a particular number of fingers and the other showing one more or less finger depending on what the first diver showed. Whether the rule is to add one or subtract one is decided before scuba diving. If there is a discrepancy in the system, nitrous narcosis is immediately suspected.